Magnetic head for perpendicular recording and magnetic disk storage apparatus mounting the head

ABSTRACT

A magnetic head is composed to diminish disordered writing bits of a recording layer or reading noise caused by a magnetic field generated from an under layer without decreasing a writing magnetic field strength of the magnetic head. The magnetic head includes a write head provided with a main pole and one or more auxiliary poles, a read head provided with a read element, and coils located on both sides of the main pole in a manner to sandwich the main pole. The coil located on one side generates the asymmetrical magneto-motive force for magnetizing the main pole to that generated by the coil located on the other side.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a magnetic head forperpendicular recording and a magnetic disk storage apparatus providedwith the head mounted thereon.

[0003] 2. Description of the Related Art

[0004] In general, the magnetic disk storage apparatus is composed sothat data may be read or written on a recording medium by using amagnetic head. In order to increase a recording density per a unit areaof a magnetic disk, it is necessary to decrease a size of recording bit.In the longitudinal magnetic recording system, however, a smallerrecording bit disadvantageously causes a recording written magnetizationon a medium to be lost by thermal fluctuation. This disadvantage bringsabout difficulty in enhancing the recording density. As the effectivetechnique in overcoming this difficulty, the perpendicular recordingsystem may be referred which is composed to record (or write) themagnetization in the perpendicular direction to the medium.

[0005] The perpendicular recording system may be roughly divided intoone system composed to have a double layered perpendicular mediumconsisting of a recording layer served as a recording medium and a softunder layer and the other system composed to have a single layeredperpendicular medium having no under layer. The system composed to usethe double layered perpendicular medium as a recording medium needs theso-called single pole type head provided with a main pole and anauxiliary pole for writing data.

[0006] The provision of the soft under layer leads to increasing awriting magnetic field strength obtained by the write head but alsoleads disadvantageously to giving rise to a failure caused by the underlayer itself. For example, magnetization on the under layer is changedaccording to the recorded bits on the recording layer and the write headfield. This change brings about a magnetic field, which may disturb thewriting bits written on the recording layer or be observed as noise whenreading the magnetizing signal with a read element. Moreover, a certainkind of distribution of the change of magnetization may bring about alarge magnetic field from the under layer.

[0007] A magnetic head having a plurality of auxiliary poles and coilshas been known, an exemplary one of which is described in the followingpatent publication 1 and non-patent publication 1. The techniquesdisclosed in these publications are prepared for a stray field and donot make any allowance for the ratio of the magneto-motive force of acoil. Further, if the head is structured to have only one auxiliarypole, the coils are located symmetrically. This structure disables tosuppress the noise caused by the change of magnetization of the underlayer.

[0008] Patent Publication 1 . . . Official Gazette of Japanese PatentLaid-open No. 2001-250204

[0009] Non-patent Publication 1 . . . Pages 163 to 168 of IEEETransactions on Magnetics. Vol.38, No.1, 2002

SUMMARY OF THE INVENTION

[0010] The magnetic field caused by the change of magnetization of theunder layer, which may disadvantageously disturb the magnetizationsignal written on a recording layer or be observed as noise when readingthe magnetization signal with the read element, leads to a greatobstacle in realizing high-density recording.

[0011] It is therefore an object of the present invention to provide toreduce the noise caused by the change of magnetization of the underlayer without decreasing the writing magnetic field strength of a writehead.

[0012] The inventors of the present invention found out the followingfact. As a result of analyzing the magnetic fluxes of the single poletype head and the under layer, it is possible to diminish the magneticflux flowing through the under layer without greatly lowering thewriting magnetic field strength as well as to suppress the disturbanceof the recorded bits and the reading noise, both of which are broughtabout by the under layer, if the coils are located on both sides of themail pole asymmetrically, concretely, the product of a number ofwindings and a current applied to the coil located on one side of themain pole is different from that of the coil located on the other sidethereof.

[0013] According to an aspect of the invention, the magnetic headincludes a write head having a main pole and one or more auxiliary polesand a read head having a read element and looped thin-film conductorcoils located on both sides of the main pole in a manner to sandwich themain pole, the magneto-motive force (product of the number of windingsand an applied current) of one coil being different from that of theother coil.

[0014] The use of the single pole type head having the coils structuredto cause the magneto-motive forces asymmetrically makes it possible toprovide the magnetic head for perpendicular recording that brings aboutno disturbance of the recorded bits and no reading noise resulting fromthe under layer. The mount of this type of single pole type head mayprovide a magnetic disk storage apparatus having a more improvedrecording density than the conventional apparatus.

[0015] Other objects, features and advantages of the invention willbecome apparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a graph useful of explaining the effect of a magnetichead according to the present invention, in which a magnetic fluxdensity of an under layer is being diminished;

[0017]FIG. 2 is a sectional model view showing a structure of a singlepole type head according to a first embodiment of the present invention;

[0018]FIG. 3 is a conceptual schematic view showing a magnetic diskstorage apparatus, for better understanding of the present invention;

[0019]FIG. 4 is a schematic view showing relation between a magnetichead for perpendicular recording and a magnetic disk, for betterunderstanding of the present invention;

[0020]FIG. 5 is a schematic view useful of better understandingperpendicular recording;

[0021]FIGS. 6A, 6B are views illustrating reduction of a magnetic fluxdensity of the under layer included in the first embodiment of thepresent invention;

[0022]FIGS. 7A, 7B are views illustrating reduction of a magnetic fluxdensity of the under layer included in the second embodiment of thepresent invention;

[0023]FIG. 8 is a model view showing the second embodiment of thepresent invention and a structure of a write and read composite headhaving a single pole type head according to the present invention;

[0024]FIG. 9 is a model view showing a third embodiment of the presentinvention and a write and read composite head having a single pole typehead according to the present invention; and

[0025]FIG. 10 is a model view showing a fourth embodiment of the presentinvention and a structure of a write and read composite head having asingle pole type head according to the present invention.

DESCRIPTION OF EMBODIMENTS

[0026] Hereafter, the present invention will be described with referenceto the appended drawings.

[0027] At first, for better understanding of the invention, theschematic composition of a magnetic disk storage apparatus will bedescribed. FIG. 3 is a schematic view showing the magnetic disk storageapparatus (in which view the magnification factors are not unified). Themagnetic disk storage apparatus is composed so that a magnetic head 14is floated on a magnetic disk 11 being in rotation when writing orreading the magnetization signal. The magnetic head 14 is mounted on aslider 13 fixed at the tip of a suspension arm 12 and is positioned by arotary actuator 15.

[0028]FIG. 4 is a schematic view showing relation between a magnetichead for perpendicular recording 14 and the magnetic disk 11 (in whichview the magnification factors are not unified, the head section isillustrated, and the main components are simplified). As is obvious fromthis figure, the magnetic head 14 is composed of a read head 16 and awrite head 18. The read head 18 is composed of two shield films locatedvertically in a manner to sandwich a read element 8. The write head 14is composed of a main pole, an auxiliary pole and a looped thin-filmconductor coil located between these poles and served as magnetizing themain pole. The upper shield layer located on the side of the write headmay be integrally formed with and served as the auxiliary pole of thewrite head.

[0029]FIG. 5 is a conceptual view showing perpendicular recording (inwhich view the head section is illustrated and the main components aresimplified). A magnetic circuit is formed so that a magnetic fieldgenerated from the main pole 1 passes through an under layer 20 andenters the auxiliary pole 3. By applying target current to a coil 2, itis possible to apply a magnetic field in a predetermined direction fromthe main pole 1 onto a recording layer 19 and then record a targetmagnetization pattern on the recording layer 19. As a magnetic diskmedium may be formed an intermediate layer between the recording layer19 and the under layer 20. The read element 7 may be a giantmagneto-resistance effect element (GMR) or a tunnel magnetic-resistanceeffect element (TMR). In FIG. 5, a numeral 17 denotes a rotatingdirection of the disk. The auxiliary pole 3 is located on the leadingside 25 of the main pole 1.

[0030] (First Embodiment)

[0031]FIG. 2 is a sectional model view showing the first embodiment of asingle pole type write head used in the present invention. In thisembodiment, the write head is composed of a main pole 1, an auxiliarypole 3 and thin-film conductor coils 2 a and 2 b located on both sidesof the main pole 1 in a manner to sandwich the main pole 1. Theschematic model view of FIG. 2 sectionally illustrates the magnetic headin the disk rotating direction from the center of the disk track, inwhich view the magnification factors are not unified. The two coils 2 aand 2 b may be composed so as to be connected in the disk rotatingdirection so that a magnetic field of the same polarity may be generatedat the tip of the main pole 1. Or, these coils 2 a and 2 b may becomposed to separate these coils 2 a and 2 b from each other so thateach coil generates the magnetic field of the same polarity at the tipthereof.

[0032] As is obvious from FIG. 2, in this embodiment, the number ofwindings of the coil 2 a located on the side where the auxiliary pole isnot provided is more than that of the coil 2 b located between the mainpole and the auxiliary pole so that the magneto-motive force of the coil2 b is greater than that of the coil 2 a. In addition, the auxiliarypole 3 may be formed integrally with and served as the upper shield ofthe read head.

[0033]FIGS. 6A, 6B show the magnetic flux density distributions of theunder layer in which the two coils have respective magneto-motiveforces, for comparing the head of the conventional structure (FIG. 6A)with the single pole type head of the present invention (FIG. 6B). InFIGS. 6A and 6B, the tones specified by the scales indicate thecorresponding magnetic flux densities, in which more dense portionscorrespond with higher magnetic flux densities. Further, in FIGS. 6A and6B, the magnetic flux density distribution shown in the right handconcerns with only the portion enclosed by the dotted line of theschematic model view of the magnetic head as viewed from the floatingsurface shown in the left hand.

[0034] In the magnetic flux density distribution shown in FIG. 6A or 6B,the real line indicates an auxiliary pole 3, while the main pole 1 isrepresented by a dot because it is too small in the scale of thesefigures. Hence, the form of the main pole 1 cannot be visible. Herein,it is assumed that the under layer 20 is composed of a material having asaturation magnetic flux density of 1.2 T. The head of the conventionalstructure (coil: 0.30 AT) shown in FIG. 6A is composed so that themagnetic flux density of the under layer reaches 1.13 T as a maximumvalue. On the other hand, in the head structure of the presentinvention, the magnetic flux density formed in the under layer reached0.59 T as a maximum value because the coils 2 a and 2 b locatedasymmetrically on both sides of the main pole 1 have the magneto-motiveforces of 0.10 AT and 0.20, respectively. In these cases, theconventional structure has a writing magnetic field strength of9.0×10⁵[A/m], while the head structure of this embodiment has a strengthof 8.5×10⁵[A/m]. That is, the reduction was less than 10%. It wasrevealed by the tones of FIG. 6B that the head structure of thisembodiment has a smaller maximum value of the magnetic flux density aswell as a smaller whole magnetic flux density of the under layer 20.This resulted in reducing the noise caused by the under layer 20.

[0035] In FIGS. 6A to 6B, the magnitude of the magnetic flux density isrepresented by variable tone and also is divided into the areas 1 to 15.

[0036]FIG. 1 is a graph that is useful of explaining the effect of themagnetic head of this embodiment. Concretely, the graph of FIG. 1 showsthe changes of maximum value of the magnetic flux density of the underlayer 20 and the write head field strength against the ratio of themagneto-motive forces of the two coils 2 a and 2 b located on both sidesof the main pole 1. The axis of ordinate represents the normalizedmagnetic flux density of the conventional structure. As is obvious fromFIG. 1, by changing the ratio of the magneto-motive forces of the twocoils 2 a and 2 b, it is possible to reduce the magnetic flux density ofthe under layer 20. For example, by making the magneto-motive force ofthe coil 2 b located on the side having no auxiliary pole 1.5 timelarger than the coil 2 a located between the main pole 2 and theauxiliary pole 3, it is possible to reduce the magnetic flux density ofthis embodiment into 60% of that of the conventional structure. Further,in this embodiment, it is preferable to keep the ratio of themagneto-motive forces of the two coils 2 a and 2 b (coil 2 b/coil 2 a)2.5 or less. If the ratio of magneto-motive force (coil 2 b/coil 2 a) is2.5 or less, the magnetic flux density of the under layer 20 may bereduced into 60% of the conventional structure as keeping the reductionof the writing magnetic field strength 10%.

[0037] Further, this embodiment is composed so that the coils 2 a and 2b have respective number of windings, that is, are locatedasymmetrically on both sides of the main pole. In place, it may becomposed so that the current values to be applied to the coils 2 a and 2b may be changed as keeping the number of windings of each coilconstant. This composition makes it possible to obtain the coilstructure in which the coils generate their respective asymmetricmagneto-motive forces. Moreover, by making the current values to beapplied to the coils 2 a and 2 b and the numbers of windings of thecoils different from each other, the coils may generate the asymmetricmagneto-motive forces.

[0038] The auxiliary pole 3 may be located on the trailing side of themain pole 1 or the leading side thereof. The auxiliary pole may beprovided on one side or both sides of the main pole so that both sidesof the main pole may have respective densities of the magnetic fluxesflown from the main pole to the auxiliary pole.

[0039] Further, the coils may be located on both sides of the main polein the track width direction.

[0040] (Second Embodiment)

[0041]FIGS. 7A, 7B show the magnetic head according to the secondembodiment of the invention. The views of these figures show themagnetic flux density distribution in the case that the distance D1between the main pole 1 and the auxiliary pole 3 (that is, the distancebetween the opposed side of the main pole 1 to the auxiliary pole 3 andthe opposed side of the auxiliary pole 3 to the main pole) is changedinto 3 μm, for comparing the head of the conventional structure (seeFIG. 7A) with the single pole type head of the present invention (seeFIG. 7B). In the conventional structure shown in FIG. 7A, by narrowingthe distance D1 more than the distance D1 of 15 μm, the distribution ofa greater magnetic flux density is made wider. On the other hand, in thehead structure of the invention shown in FIG. 7B, even if the distanceD1 between the main pole 1 and the auxiliary pole 3 is made narrower,the magnetic flux density of the under layer 20 is made smaller.

[0042] In FIGS. 7A and 7B, the magnitude of the magnetic flux density isrepresented by variable tones and also is divided into the areas 1 to15.

[0043] Hence, as shown schematically in FIG. 8 (schematic section of thetrack center in the disk rotating direction), the head structure of theinvention allows the distance D1 between the main pole and the auxiliarypole (between the opposed side of the main pole 1 to the auxiliary pole3 and the opposed side of the auxiliary pole 3 to the main pole) to benarrowed to a film thickness T1 of the coil 2 a and a film thickness T2of an insulating layer (served as insulatively separating the coil 2 afrom the main pole 1 and the auxiliary pole 3) without having toincrease the magnetic flux density of the under layer 20. That is, thedistance between the main pole and the auxiliary pole may be madesmaller to [number of coil layers×T1+(number of coil layers+1)×T2]. Thethickness T2 of the insulating layer may be made smaller to 100 nm inconsideration of its pressure resistance. This makes it possible tonarrow a distance D3 between the read element 7 sandwiched between alower shield 8 and an upper shield 9 to the opposed side of the mainpole 1 to the read element. Thus, as shown in FIG. 8, this embodimentmay offer a read and write composite head that is suitable to thehigh-density recording. In addition, in FIG. 8, the auxiliary pole 3 maybe integrally formed with and served as the upper shield 9.

[0044] (Third Embodiment)

[0045]FIG. 9 is a schematic sectional view showing a magnetic headaccording to a third embodiment of the present invention, in which viewthe read element 7 and the auxiliary pole 3 are located in a manner tosandwich the main pole 1 and the coils are located on both sides of themain pole in an asymmetrical manner, that is, in a manner to applyrespective magneto-motive forces onto both sides of the main pole asdescribed with respect to the foregoing first and second embodiments.The section is cut on the center of the track in the disk rotatingdirection.

[0046] In this embodiment, no auxiliary pole 3 is provided between theread element 7 and the main pole 1, so that the distance D3 between theread element 7 and the opposed side of the main pole 1 to the readelement 7 may be made narrower by the film thickness. Moreover, sincethe magnetic flux being flown from the main pole 1 to the upper shield 9is suppressed, it is preferable to make the distance D2 between theupper shield 9 and the main pole 1 (in particular, the distance betweenthe opposed side of the upper shield 9 to the main pole and the opposedside of the main pole 1 to the upper shield) greater than the distanceD1 between the opposed side of the main pole to the auxiliary pole andthe opposed side of the auxiliary pole to the main pole.

[0047] Further, in order to suppress the magnetic flux being flown intothe upper shield 9, in this embodiment, it is preferable to make aproduct (μa/D1) of an inverse of the distance D1 and a permeability μaof the auxiliary pole 3 greater than a product (μs/D2) of an inverse ofthe distance D2 and a permeability μs of the upper shield, the distanceD1 meaning a spacing between the main pole and the auxiliary pole,concretely, the opposed side of the main pole 1 to the auxiliary poleand the opposed side of the auxiliary pole to the main pole and thedistance D2 meaning a spacing between the main pole and the uppershield, concretely, between the opposed side of the upper shield film 9to the main pole and the opposed side of the main pole 1 to the uppershield film.

[0048] In addition, in this embodiment, the trailing side may bereversed in position to the leading side.

[0049] (Fourth Embodiment)

[0050]FIG. 10 is a schematic sectional view showing a magnetic headaccording to a fourth embodiment of the present invention. The sectionis cut on the center of the track of the head in the disk rotatingdirection. In this embodiment, the auxiliary poles 3 a and 3 b arelocated on the trailing side and the leading side in a manner tosandwich the main pole 1. The coil 2 c is located between the main pole1 and the auxiliary pole 3 a and the coil 2 d is located between themain pole 1 and the auxiliary pole 3 a. The opposed area of theauxiliary pole 3 a to the floating surface is made greater than theopposed area of the auxiliary pole 3 b to the floating surface and themagneto-motive force of the coil 2 c, which corresponds to a product ofthe number of windings of each coil 2 c located on the side of theauxiliary pole 3 a with a smaller area and a current applied to thecoil, is made greater than the magneto-motive force of the coil 2 dlocated on the auxiliary pole 3 b with a larger area. The resultingcoils generate the asymmetrical magneto-motive forces.

[0051] In this embodiment, the magneto-motive force of the coil 2 clocated on the leading side is greater than, that is, asymmetrical tothat of the coil 2 d located on the trailing side. Hence, the filmthickness t2 of the auxiliary pole 3 a located on the leading side ismade thinner than the film thickness t1 of the auxiliary pole 3 blocated on the trailing side. This allows the distance between the readelement 7 and the main pole 1 (concretely, between the read element 7and the opposed side of the main pole 1 to the read element) to benarrowed accordingly. The resulting composition offers the read andwrite composite magnetic head that is suitable to the high-densityrecording.

[0052] In addition, in this embodiment, the trailing side may bereversed in position to the leading side.

[0053] (Fifth Embodiment)

[0054] This embodiment concerns a magnetic disk storage apparatus whichis suitable for high-density recording. The magnetic disk storageapparatus includes a magnetic head of the invention, the magnetic headhaving a main pole, at least one auxiliary pole, and coils each composedof a thin-film conductor coil that are located in a manner to sandwichthe main pole and to make the magneto-motive force of the coil locatedon one side different from that of the coil located on the other side; amagnetic disk medium composed of a soft under layer and a recordinglayer laminated thereon; a magnetic circuit arranged to be opposed tothe magnetic disk medium rotating on the magnetic head and cause themagnetic field coming from the main pole to enter into the auxiliarypole through the recording layer and the under layer, the magnetic fieldcoming from the main pole being applied into the recording layer bypassing current through the coils for writing a magnetizing signal.

[0055] As set forth above, the magnetic head for perpendicular recordinguses the structure of the coils asymmetrically located on both sides ofthe main pole, which includes the write head having the main pole andone or more auxiliary poles, the read head provided with the readelement, and coils each composed of a thin-film conductor being locatedon both side of the main pole, the magneto-motive force of the coillocated on one side being different from that of the coil located on theother side. This coil structure makes it possible to reduce the magneticflux density flowing through the under layer and thereby to diminish thenoise generated by the under layer without deteriorating the writingmagnetic field strength generated by the main pole.

[0056] It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

What is claimed is:
 1. A magnetic head comprising: a main pole; one or more auxiliary poles; and coils each composed of a looped thin-film conductor coil, said coils being located on both sides of said main pole in a manner to sandwich said main pole; and wherein said coil located on one side generates different magneto-motive force from that of said coil located on the other side.
 2. A magnetic head as claimed in claim 1, wherein said auxiliary pole is located only on one side of said main pole so that the magneto-motive force of said coil located on the side having no auxiliary pole may be greater than that of said coil located on the side having said auxiliary pole.
 3. A magnetic head as claimed in claim 1, wherein the ratio of the magneto-motive forces of said coils located on respective sides is 1.5 or more.
 4. A magnetic head as claimed in claim 1, wherein the ratio of the magneto-motive forces of said coils located on respective sides is 2.5 or less.
 5. A magnetic head as claimed in claim 1, wherein said auxiliary pole is located only on one side of said main pole so that a value of current applied into said coil located on the side having no auxiliary pole may be greater than a value of current applied into said coil located on the side having said auxiliary pole.
 6. A magnetic head as claimed in claim 5, wherein a ratio of applied current values of said coils located on respective sides is 1.5 or more.
 7. A magnetic head as claimed in claim 5, wherein a ratio of applied current values of said coils located on respective sides is 2.5 or less.
 8. A magnetic head as claimed in claim 1, wherein said auxiliary pole is located only on one side of said main pole and the number of windings of said coil located on the side having no auxiliary pole is greater than that of said coil located on the side having said auxiliary pole.
 9. A magnetic head as claimed in claim 8, wherein a ratio of the number of windings of said coils located on respective sides is 1.5 or more.
 10. A magnetic head as claimed in claim 8, wherein a ratio of the number of windings of said coils located on respective sides is 2.5 or less.
 11. A magnetic head comprising: a main pole; one or more auxiliary poles; and coils each composed of a looped thin-film conductor coil, said coils being located on both sides of said main pole in a manner to sandwich said main pole; and wherein said coil located on one side is caused to generate magneto-motive force for magnetizing said main pole that is asymmetrical to that generated by said coil located on the other side.
 12. A magnetic head as claimed in claim 1, wherein a distance between said main pole and said auxiliary pole is twice or less as long as the thickness of each coil located between said main pole and said auxiliary pole.
 13. A magnetic head comprising: a read and write composite head having; said magnetic head claimed in claim 1 being served as a read head, and a read head composed of a read element and two shield films located in a manner to sandwich said read element.
 14. A magnetic head as claimed in claim 13, wherein an auxiliary pole that is one of the components of said read head is formed integrally with and uses one of said shield films composing said read head.
 15. A magnetic head as claimed in claim 13, wherein said read head is located on the opposite side to said auxiliary pole in a manner to sandwich said main pole.
 16. A magnetic head as claimed in claim 15, wherein a distance between said main pole and said auxiliary pole is smaller than a distance between said main pole and said shield film closer to said main pole.
 17. A magnetic head comprising: a main pole; auxiliary poles; coils; and said auxiliary poles and said coils being located on a trailing side and a leading side in a manner to sandwich said main pole, the opposed area of one auxiliary pole to a floating surface being made smaller than the opposed area of the other auxiliary pole to said floating surface, and the magneto-motive force of said coil located on the side of said auxiliary pole with a smaller area being made greater than that of said coil located on the side of said auxiliary pole with a larger area.
 18. A magnetic head as claimed in claim 17, wherein the current applied to said coil located on said auxiliary pole with a smaller area is greater than the current applied to said coil located on said auxiliary pole with a larger area.
 19. A magnetic head as claimed in claim 17, wherein the number of windings located on said auxiliary pole with a smaller area is greater than that located on said auxiliary pole with a larger area.
 20. A magnetic head comprising: a read and write composite head having; a magnetic head described in claim 17 being served as a write head; a read head composed of a read element and two shield films located in a manner to sandwich said read element; and said read head being located on the side of said auxiliary pole with a smaller area. 